1. Field of the Invention
The present invention generally relates to a method for providing an output image in either a Cylindrical mode or a Perspective mode, more particularly to a method that transforms an image in one of Azimuthal modes to an image in either a Cylindrical mode or a Perspective mode.
2. Description of the Prior Art
Image systems that utilize wide-angle lenses for quite a while, more particularly, a 180-degree fisheye lens is known in the art already. A fisheye lens generates images that are related to a hemisphere, a partially hemispherical, and field of view in those arts. That is, a wide-angle lens allowess a large viewing angle relative to views obtained by an ordinary camera lens. An image obtained by a wide-angle lens, however, contains radial barrel distortion as always.
In order to correct image distortion during image captured, most immersive viewers perform a geometric transformation process on a representation of the source images. This process of transforming distorted images to accurate Perspective images is referred to as “Perspective correction” or “dewarping”. Perspective correction restores the scene to proper Perspective mode based upon the orientation by the image viewing position.
It is well document for method and device for selecting and undistorting the portion of a fisheye image. Such conventional method and device, however, suffer from a larger number of limitations. For example, (1) Hemisphere model is mathematically limited by 180 degrees. (2) Perspective view is with distortion increased when a viewing position approached to 180 degree. (3) It's impossible to generate 180 degree or above Perspective view. (4) Hemisphere is not good enough to describe a real fisheye lens or a wide-angle lens. (5) Perspective view presents an undistorted view of a portion of a fisheye image, they do not allow a viewer to observe simultaneously the relation of the undistorted view to entire image.
Accordingly, there is a need of adaptive method and apparatus for acquiring and viewing a wide-angle image that provides. (1) The limitation of the DOV of 180-degree Lens should be relax, more particularly, the lens degree of view is able to going up to 360 degrees. (2) Entire projection is from a wide-angle image. (3) An adaptive method is to describe the real wide-angle lens. (4) A projection could project an entire wide-angle image to an object image while distortion is corrected or reduced.
It is important to have a method for selecting and dewarping enhanced Images taken from a wideangle lens, especially a fisheye lens.